Many low water sensing systems utilize a probe that completes an electric circuit through the boiler water in order to sense the presence or absence of boiler water. A simple sensing circuit is impractical due to the foaming, boiling, and movement of the boiler water when a boiler is in use. A simple probe for sensing the establishment or interruption of an electric circuit has the practical defect of being unreliable, and can cause nuisance shut downs of the boiler operated system.
Attempts to overcome this problem have been made in the past by the use of fixed time delay mechanisms. Such a time delay system is shown in the J. I. Bartels U.S. Pat. No. 4,360,738, and assigned to the assignee of the present invention. This United States patent shows an attempt to solve this problem by the use of a fixed electronic type timer. This type of system may be utilized in some applications, but fixed time delays can create unsatisfactory operation in other applications. The turbulence within the boiler is therefore, an ongoing type of problem to the industry.